1. Field of the Invention
This invention relates to a control system for internal combustion engines for automotive vehicles, which incorporates a DBW (Drive By Wire) system for electrically controlling the opening of a throttle valve of the engine in response to a stepping amount of an accelerator pedal of the vehicle.
2. Prior Art
Conventionally, a control system for internal combustion engines for automotive vehicles has been proposed by Japanese Laid-Open Patent Publication (Kokai) No. 53-40128, which is intended to prevent deterioration of a catalytic converter of the engine during the operation of the engine in a high-speed and high-load condition, and controls the air-fuel ratio of a mixture supplied to the engine to a richer value than a stoichiometric air-fuel ratio to effect so-called fuel injection cooling, thereby controlling the temperature of the catalytic converter to a value lower than a predetermined value when the engine is operating under such a high-speed and high-load condition.
However, according to this technique, the air-fuel ratio of the mixture deviates toward a richer side of the stoichiometric air-fuel ratio, so that the purifying efficiency of the catalytic converter can be lowered, causing increased emission of noxious components of exhaust gases.
Further, the fuel supply amount is increased, which results in an increase in the fuel consumption.